Dodecahema Leptoceras (Slender-Horned Spineflower)
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Dodecahema leptoceras (slender-horned spineflower) 5-Year Review: Summary and Evaluation [Photo or illustration, if available] Dodecahema leptoceras (slender-horned spineflower). Photocredit: Mark W. Skinner (USDA-NRCS PLANTS Database) U.S. Fish and Wildlife Service Carlsbad Fish and Wildlife Office Carlsbad, California October 1, 2010 1 2010 Slender-horned Spineflower 5-year Review 5-YEAR REVIEW Dodecahema (Centrostegia) leptoceras (slender-horned spineflower) I. GENERAL INFORMATION Purpose of 5-Year Reviews: The U.S. Fish and Wildlife Service (Service) is required by section 4(c)(2) of the Endangered Species Act (Act) to conduct a status review of each listed species at least once every 5 years. The purpose of a 5-year review is to evaluate whether or not the species’ status has changed since it was listed (or since the most recent 5-year review). Based on the 5-year review, we recommend whether the species should be removed from the list of endangered and threatened species, be changed in status from endangered to threatened, or be changed in status from threatened to endangered. Our original listing of a species as endangered or threatened is based on the existence of threats attributable to one or more of the five threat factors described in section 4(a)(1) of the Act, and we must consider these same five factors in any subsequent consideration of reclassification or delisting of a species. In the 5-year review, we consider the best available scientific and commercial data on the species, and focus on new information available since the species was listed or last reviewed. If we recommend a change in listing status based on the results of the 5-year review, we must propose to do so through a separate rule-making process defined in the Act that includes public review and comment. Species Overview: Dodecahema leptoceras (slender-horned spineflower) is a small annual plant in the Polygonaceae (buckwheat family). It has been federally and State listed as endangered since the 1980s. The species is usually found in drought prone alluvial benches subject to only rare flood events. At the time Dodecahema leptoceras was listed (as Centrostegia leptoceras) it was only known to be extant at 5 locations representing 6 element occurrences (EOs). More intensive surveys and resurveys of historical occurrence sites have detected additional extant occurrences since listing for a total of 20 extant occurrences. At listing, development, mining activities, off- road vehicles, proposed flood control measures, and trash dumping were among the threats cited. Occurrences of Dodecahema leptoceras are currently threatened by development, mining activities, flood control measures, and trash dumping. Methodology Used to Complete This Review: This review was conducted by Gary D. Wallace and staff at the Carlsbad Fish and Wildlife Office (CFWO), following the Region 8 guidance issued in March 2008. We used information in the 1987 listing rule, available literature, and reports and information in our files. We also relied upon information provided by experts familiar with the species, its habitat, and the associated processes. This 5-year review contains updated information on the species’ biology and threats, and an assessment of that information compared to that known at the time of listing, since the last 5-year review, or since the last document containing a five-factor analysis. We 2 2010 Slender-horned Spineflower 5-year Review focus on current threats to the species that are attributable to any of the Act’s five listing factors. The review synthesizes all this information to evaluate the listing status of the species and provide an indication of its progress towards recovery. Finally, based on this synthesis and the threats identified in the five-factor analysis, we include a prioritized list of conservation actions recommended to be completed or initiated within the next five years. These actions are designed to alleviate persisting threats to the taxon. Contact Information: Lead Regional Office: Larry Rabin, Deputy Division Chief for Listing, Recovery, and Habitat Conservation Planning, Region 8; (916) 414-6464. Lead Field Office: Gary D. Wallace, Botanist and Bradd Baskerville-Bridges, Recovery Branch Chief; Carlsbad Fish and Wildlife Office; (760) 431-9440. Cooperating Field Office: Chris Dellith, Ventura Fish and Wildlife Office; (805) 644- 1766. Federal Register (FR) Notice Citation Announcing Initiation of This Review: The notice announcing the initiation of this 5-year review and opening a 60 day period to receive information was published on March 22, 2006 (USFWS 2006a, p. 14538). A notice announcing corrections to the March 22, 2006 notice was published on April 3, 2006 (USFWS 2006b, p. 16584). We received one letter providing information on Dodecahema leptoceras. Information received will be discussed in the relevant sections of this review. Listing History: Original Listing FR Notice: 52 FR 36265 Date of Final Listing Rule: September 28, 1987 Entity Listed: Dodecahema (Centrostegia) leptoceras (slender-horned spineflower), a plant species. Refer to section on Taxonomy and Nomenclatural changes. Classification: Endangered State Listing Dodecahema leptoceras was listed (as Centrostegia leptoceras) (slender-horned spineflower) as an endangered species under the California Native Plant Protection Act (NPPA) in 1982, and under the California Endangered Species Act (CESA) in 1987. Associated Rulemakings: None. Review History: A notice initiating a status review of Dodecahema leptoceras was published on November 9, 1991 (USFWS 1991, p. 56882). The results of this review were not published; however, our 3 2010 Slender-horned Spineflower 5-year Review recommendation was no change in status (USFWS 1992, p. 1). No subsequent 5-year review for D. leptoceras was initiated since that time until this current 5-year review. Species’ Recovery Priority Number at Start of 5-Year Review: The Recovery Priority Number for Dodecahema leptoceras was reported as 1C in the 2010 Recovery Data Call for the CFWO. This number indicates that the species is in a monotypic genus (i.e., a genus with a single recognized species) has a high degree of threat and a high potential for recovery. The recovery priority number is based on a 1-18 ranking system where 1 is the highest-ranked recovery priority and 18 is the lowest (USFWS 1983, p. 43098). The “C” indicates conflict with construction or other development projects or other forms of economic activity. Recovery Plan or Outline: No recovery plan has been developed for this species. II. REVIEW ANALYSIS Application of the 1996 Distinct Population Segment (DPS) Policy: The Act defines species as including any subspecies of fish or wildlife or plants, and any distinct population segment (DPS) of any species of vertebrate wildlife. This definition of species under the Act limits listing as distinct population segments to species of vertebrate fish or wildlife. Because the species under review is a plant the DPS policy is not applicable to the species’ listing is not addressed further in this review. Information on the Species and its Status: Little background information was provided in the final listing rule. Therefore, the following sections on species description, biology and life history, distribution, abundance and population trends, genetics, and habitat conditions include information available at the time of listing as well as more recent information. Species Description Dodecahema leptoceras is an annual plant in the Polygonaceae (buckwheat family). Plants have a distinctive basal rosette of leaves ranging from 3 to 8 centimeters (cm) (1.2 to 3.1 inch (in)) in diameter. The leaves frequently become reddish at maturity. The flower stalks are branched and erect 3 to 10 cm (1.2 to 4 in) tall (Reveal and Hardham 1989, p. 87). Flowers are arranged in clusters along the flower stalks and each cluster is surrounded by an involucre (a ring of modified leaves beneath a flower cluster). Characteristic of this species, each of the 6 involucre segments has an awn at its base as well as at its apex. This feature distinguished this genus from the closely related genera Chorizanthe and Centrostegia (Reveal and Hardham 1989, p. 86). The flowers are white to pink, 1.2 to 2 millimeters (mm) (0.5 to 0.8 in) long, each producing a single achene (a dry single-seeded fruit), 1.7 to 2 mm (0.06 to 0.08 in) long. 4 2010 Slender-horned Spineflower 5-year Review Dodecahema leptoceras plants are difficult to identify with certainty, especially in the field, and may be confused with similar-looking, often co-occurring, related taxa (e.g., Chorizanthe leptotheca (peninsular spineflower). For these reasons, reports of occurrences that lack voucher collections or reference data may not be reliable. Species Biology and Life History Dodecahema leptoceras is found in drought prone habitats where germination is likely related to rainfall. Individual plants are difficult to detect because they are small and occur in relatively small, isolated patches across often extensive floodplain habitat. Additionally, plant densities may be low during drought conditions. At the time of listing, little was known about the species’ biology and life history. Information developed since the species was listed is described below. Dodecahema leptoceras germinated by late February at several study sites in 1995 and 1996 (Ferguson et al. 1996, p. 10). Survival to flowering was highly variable (Ferguson et al. 1996, p. 11). The greatest number of plants survived to flowering stage (about 60 percent of the study sample) during unusually cool and wet seasonal conditions and the least (about 6 percent) survived during drought conditions. The number of seeds produced per plant ranges from three to 507 (Ferguson 1999, p. 28) and is likely related to annual environmental conditions. Plenoculus davisii, a native wasp, was identified as a potential pollinator (Ferguson et al. 1996, p. 14). The involucres (united bracts), each containing three flowers, are armed with small spines and hooks that are likely effective for dispersal by small animals.